Notch codes for a transmembrane receptor which mediates the differentiation of the nervous system as well as a variety of other tissues involving regulative decisions during Drosophila development. The overall aim of this proposal is to contribute to the dissection of the Notch pathway. Within this framework, we are specifically interested in addressing the function of the intracellular domain of the Notch molecule in an attempt to gain insight into the nature of the signal that the Notch receptor mediates. Several genetic screens are proposed in order to identify interaction partners of Notch and the molecular characterization of these partners is anticipated. In addition a documented molecular interaction between the intracellular domain of Notch and one of its genetic interaction partners deltex and suppressor of Hairless, will be further characterized. Finally, genes which are capable of interacting with deltex will also be identified and characterized.